Trimming attachment for sewing machines



Oct. 12, 1943. A. KROHN wnnmme ATTACHMENT FOR SEWING MACHINES Filed Sept. 17, 1940 2 Sheets-Sheet 1- Oct'. 12, 1943. A. KROI -IN TRIMMING ATTACHMENT FOR SEWING MACHINES Filed Sept. 17, 1940 2 Sheets-Sheet 2 Patented Oct. 12, 1943 UNITED STATES PATENT TRIMIWING ATTACHMENT FORSEWING MACHINES Arnold Krohn, Brockton, Mass. V Application September 17, 1940, Serial No. 357,166

13 Claims.

The main object of this invention is to provide a simple and effective trimmer for application to sewing machines for the purpose of trimming the edge of a piece of work while stitches are being formed and placed in the work. One important use for such a trimming device is to cut off the edges of the linings or inner facings of shoe uppers at the same time that such linings are stitched to those edges of the shoe upper which are exposed to view in the finished shoe. A lining or facing of leather is ordinarily provided at the margins of the upper, and the edges of the upper leather are folded inward and stitched to such lining on a line parallel to the fold. Such folding gives a finished character to the exposed edges of the upper. Commonly the lining is trimmed close to the seam and slightly within the finishing edge fold of the upper leather in order not to impair this finished appearance.

Trimmers have heretofore been provided for this purpose with capacity for being put out of action when their use is not required, and for locating the knife in a position where it will not interfere with the sewing of other seams in parts of an upper, or other work piece, where trimming is not required. The most commonly used trimming attachments'of the prior art are more or less cumbersome and bulky and have parts projecting for such a distance laterally from the location of the needle as to make difiicult the manipulation'of such work as a shoe upper in the manner necessary for trimming the lining at all of the edges where trimming is needed. An important part of my object is to eliminate such defects and provide a trimmer and means for putting it into and out of action which is devoid of projections liable to interfere with the manipulation of the work. Another object is to provide a simpler means for operating the trimming knife and for putting the knife into and out of action at the will of the operator, than those heretofore known, and one which can be applied to existing commercial sewing machines with a minimum of difficulty and without deranging the stitch-forming and work-feeding instruments of the machine or the mechanisms by which such instruments are operated.

. It is to be understood that the mention herein of one important use for my invention is not a limitation. of the scope in which I claim patent protection; but that all uses which the device herein disclosed is capable of serving, and all equivalents of this particular disclosure are included within .the protection hereby claimed.

The nature of the invention and the particuon the lines i4 and 5 5 respectively of Figlars in which it exists canbest be explained by the description of one concrete embodiment thereof with referenceto the drawings in which such embodiment is shown.

In the drawings Figure 1 is a front elevation of a sewing machine in which the invention; is applied. Figure 2 is a similaryiew on a larger scale of the work-supporting post at the forward end of the machine, in and on which the trimmer and the means for putting it into and out of action are mounted. i a

Figure 3 is a plan view of the post and external parts mounted thereon shown in Figure 2. Figures 4 and 5 are detail sectional views taken ure 2.

Figure 6 is a detail horizontal section taken. on the line 66 of Figurel;

Figure '7 is in part a side elevation of the work-supporting post and in part a vertical sec tion taken on line 'l--'l of Figure 2. U 1

' Figure 8 is a vertical section taken on line 8-8 of Figure '7, viewed in the direction of the arrows, and showing the trimming knife in elevation. p I g Figure 9 is a large scale :view of the parts ,shown in section in theupper portion of 'Figure 7, showing the trimming knife in action forcutting off the edge of a shoe upper lining.

s Figure 10 is a view similargto Figure *9 showing the trimming knifeout of action andlocated in a position where it is clear of any interference with a work piece supported on the post. I

Fig, 11 is a perspective view of the trimming knife. j. 1

Like referencesindicate the same parts whereever they occurin all of the figures. j I

The front elevation of a standard sewing ma chine is illustrated in Figural. The reference number H represents the base supported'on feet I2. A column 13 rises from the rearend of the base and supportsan overhanging arm terminating in a head hi in which the-, reciprocating needle bar 15 and presser bar 16 *aremounted. A work-supporting post ll risesfrom the base beneath the head l i'and containsa. feedflever l8 (Figure 7) mounted'to oscillate upon a pivot l9. In the present illustration said feed lever is substantially vertical and'its pivot is substantially horizontal. Its upwardly extending arm carries a feeder plate '20 having a serrated .upper edge projecting through a slot2l in a work supporting plate 22 mounted on the upper endof the post. The upper surface oflthe plate 22,

whereon work is laid for stitching and trimming is substantially horizontal; and both this surface and the serrated edge of the feeder plate are sufficiently far removed from the pivot l9 to cause the feeding and return movements of the edge serrations to occur in a path of which the divergence from a substantially horizontal straight line is inappreciable. The presser bar l6 and presser foot 23, the needle bar l5, needle 24 and cooperating stitch-forming instruments, the feeder, and the mechanisms for operating these instruments are all standard parts of a.

commercial sewing machine and require no further illustration herein. The trimming apparatus in which the invention resides is independent of the details of such instruments and mechanisms, and may be employed in machines in which such instruments and mechanisms are of various characters.

A knife 25 is the trimmer or trimming instrument of this machine. It is provided with a cutting edge 26 adapted to reciprocate in a position crossing, and in contact with, the rear bounding edge 21 of the work supporting surface of plate 22. In the form shown here the knife is a bar of suitablematerial having its cutting edge provided on one end and having an integral lip 28 extending beyond and to one side of the cutting edge 26 in a location such as to hold the overlying piece away from the cutting edge while being stitched to an underlying piece and while the knife is trimming the edge of the under piece.

The knife is provided with a shank 29 of dovetail cross section; such shank being preferably formed by bending a portion of the knife bar at right angles to that portion on the end of which the cutting edge is located. One beveled face of shank 29 occupies an undercut guideway in a carrier block or holder 30, as shown in Fig. 4, and the opposite beveled face of the shank is engaged by a clamp 3| having a shank 33 which extends through the block and on which is threaded a nut 32 whereby the clamp may be set up against the shank. The holder 30 has an arm 34, of dovetail section offset from the above named guideway and extending in a direction substantially perpendicular to the shank 29 and parallel to that part of the knife which carries the cutting edge. Arm 34 is fitted in a horizontal guideway in the forward side and near the upper end, of a lever 35 to which it is secured adjustably by screws 38 passing into the lever through slots in the arm.

Lever 35 in turn is connected by a pivot pin 31 to a support 38 constructed as a slide which is fitted between parallel upright guiding surfaces 39 and 40 inthe inner or rear face of the detachable front plate 4| of post H. The axis of pivot 31 is parallel to the axis of pivot I; in other words, is substantially horizontal, and is comparatively near the latter axis; as near as feasible to permit its up and down movement with the supporting slide 38 without interference.. The levers 35 and I8 are substantially parallel and they oscillate in parallel planes about their respective pivots. Although the knife carrying lever 35 is in front of the feeder lever l8, the offset formation of the knife holder 36 brings the knife itself to a position in rear of the feeder plate 20 and against the rear edge of the work support. The knife is at such a distance from the pivot 31 that its reciprocating movements, through the short distance which suffices for trimming in machines in this chaliii acter, are approximately straight and parallel to the upper surface or plane of the supporting plate 22, and parallel likewise to the movements of the feeder 20.

The manner in which the knife is connected to its carrier lever 35, by means of the intermediate holder 30, enables the knife edge to be adjusted to the proper height with respect to the work support and to the proper position with respect to the needle; and to be readjusted when its cutting edge recedes due to sharpening. The correct position of the cutting edge when the knife is in action, is beside the location of the needle; that is, approximately in a line from the needle perpendicular to the direction of feeding impulses applied to the work; and the knife is reciprocated so that the cutting edge 25 moves back and forth across such perpendicular line in a path of which all points lie in a plane parallel to the feed of the work.

Said cutting edge is preferably slanted at an acute angle to the overhanging lip 28 and ex tends substantially up to that lip. It cuts the work by virtue'of relative movement between the knife and work piece along the line of feed. Fig. 9 illustrates the manner of operation in trimming a shoe upper lining, for instance. There a represents a portion of a shoe upper, b a portion of the contiguous lining, and c the edge fold of the upper. The folded edge is stitched to the lining by a seam d, and in the course of stitching the knife trims the lining at a distance from the seam determined by the distance of the edge 21 and the knife from the location of the needle. The separating lip 28 enters between the edge of the upper and the lining, holding the upper away from the cutting edge so that it is not marred and holding down the lining so that the latter is not raised by the inclined cutting edge, but is properly cut.

Oscillating movement is imparted to the knifecarrying lever 35 by means of a driver consisting of a lever arm 42 and a coupling pin 43 carried by said arm and projecting into a slot 44 in the arm 35a of the lever 35. The arm 42 is secured and keyed to one end of a rockshaft 45 which is mounted to turn in bearings 46 secured to the machine base II in the front of the post. An arm 41 is clamped about the rockshaft and extends downward through an opening in the base, having a fork 48 on its lower end which embraces a cam 49 on a cam shaft 50. Said shaft 50 is a standard part of the commercial sewing machine, and may be a part of the means by which oscillating movement is given to the feed lever. Its other functions are immaterial to the explanation of the present, invention. The only material fact is that an existing shaft of the commercial machine is utilized for imparting oscillating movement to the trimming knife.

The slide 38 may be raised and lowered. When raised, it places the trimming knife in the operative position shown in Figures 2, 3, '7', 8 and 9, in which the cutting edge of the knife crosses the plane of the work-supporting surface and rises a height above such plane substantially equal to the thickness'of a work piece, such as the shoe upper lining 17 shown in Figure 9. When lowered, it coactswith other means presently described to place the knife in the inoperative position shown in Figures 1 and 10, in which the knife and its guard lip 28 are wholly below the supporting surface of the plate 22, or, atleast, are depressed as far as not to interfere with the work. A compression spring 51 secured 'engagementwith the lever arm 35a. The cam to the plate 4| byscrewT52 enters a isocketim -in-the slide 38 and tends constantly to depress the slide, being put under increased compression when the slideis raised. .A second compression spring 530, confined at one end in a socket54 inla portion of the slide 38, and at the other 'end in a. socket 55 in the arm 35aiofthe knifeoperating lever, tends constantly to move said lever from the full-line position to'the dottedline position shown in Figure 8, and thereby to retract the knife from its position abreast of the needle. That portion of the edge 21 of the supporting plate 22 which lies beside the retracted position of the knife (it is designated as 210. in Figure 3) is slightlyinclined away fromthe path of the knife to permit unobstructed descent of the knife when so retracted, and to cause the knife edge to come into bearing with the parallel portion of the edge 27 when the knifeis raised and advanced to cutting position.

To raise the slide 38 and permit its descent,

I have provided a lifter 56; and to permit .re-

traction of the knife by means of--the spring 530'in the manner described,'I have provided means for disengaging thepin 43 from the slot 44. Such disengagement is necessary also to prevent imparting of motion to the knife by the constantly vibrating arm 42 when stitching is performed without trimming.

I The pin '43 is slidingly mounted in a thimble '57 which is screwed into a tapped hole through the arm 42,

j and a spring 58 reacts between "a Wall or flange "at the outer end ofsaid thimble and a shoulder ries an upstanding projection 63 having a cam= 'or wedge surface 64 (Figure 6) at the side adjacent to the post. Rotation of the sleeve is prevented, and the projection 63 is maintained in its upright position, by a guide bracket 65 secured to the arm 42 and projecting outwardly therefrom parallel to the axis of the thimble 51 in engagement with a fiat surfaced projection 66 on the under part of the sleeve 6|.

The lifter 56 is a cam disk pivoted on a stud 61 which is mounted in the front side of the plate M of the postpand projects forward. The upper part of the periphery of the lifter disk has a cam portion 68 adapted to pass under and aside from a pin 69 which projects forwardly from the slide 38; the rise and descent of such cam being suificient to bring the knife into the operative raised position and to permit its descent into the inoperative position. Adjacent to this cam surface the lifter has a supporting edge!!! of uniform radius in which there is a shallow notch H adapted to receive pin 69 and having-a described, and carries in an adjustable manner a displacement cam l4 having a wedge surface 15.

This latter is suitably located to pass into en *gagement with, and displace outwardly, the pro- J'ection 63 when the lift'eriis turned counterclockwise from the position shown in Figure 2' to that shown in Figurel and the rise of wedge is suificient to withdraw .pin 13 wholly'from surfaces 68 and limay be located to come into and out of engagement, one with the pin 69' and the'other with the projectionv 63, simultaneously; but this isnot an essential feature. It is only necessary. that the cam 14 be wholly withdrawn from the projection 63 when the pin 69 is in the notch H, and that the lifter be clear of this pin when the cam 14 is in retracting engagement with the projection 63. When the latter condition obtains, the knife is retracted anddepressed by the joint action of spring 5|, gravity,

and spring 530.

'- 'In this condition, the slot 44 is atone side of .bring this slot within the range of the. pin when "the knife is raised by the cam 68.. and the pin the'limits of oscillation ofpin 43. In order to released from the restraint of cam it, the lifter -56 is provided with a rearwardly projecting stud 76, and the lever 35a is provided with a forwardly projecting stud ll. These studs areat approximately equal distances from the axis of pivotlil, and otherwise so located that, when the lifter is turned clockwise from. the position shown in Figure 1 to the brokenline position shown inFigure 2, the stud 16 will engage the stud" and move the lever to the point where its slot 44 is within the limits of oscillation of the pin 43. Thus, to put the knife into action, the operator swings'the'arm F2 from thepositionof'the lifter, the stud 16 is clear of the stud Tl. 1 When the knife is in operation, its cutting edge bears against the edge 21 of the work-supporting plate, whereby the latter edge cooperates with the cutting edge in obtaining a smooth clean cutting effect. This relationship is in part effected by the disposition ofthe knife-carrying lever andis reinforced by forward pressure exerted by the feeder plate 28 on the knife carrying lever 35 through a stud 18 which is secured to the lever 35 and bears at its rear end against the forward side of the feeder plate. Said stud is not secured to the'feeder plate but bears slidingly thereon, whereby both the lever and the feeder plate are free to move in their prescribed planes independently of one another.

This trimming mechanism gives cutting and return movements to the knife in a path parallel to the direction in :which feeding impulses are applied to the work. The cutting motion is therefore in effect a straight line movement, for the arc of movement around the pivot 31 is of no effect, being in a plane perpendicular to the I work. Such straight line movement, and the'lo- 60" cation of the cutting path directly beside the position of the needle, ensures continuity of successive cuts, whereby the resultant trimmed edge (whether straight, convex or concave). is substantially smooth and continuous, with no distinct jagged points or serrations. When the knife is made inoperative, it is put out of the way where it oifers no impediment whatever to the placing of stitches in work at any distance from the edges of the work. The means for putting the trimmer into and out of action are ef-, 'ficient, easily and instantaneously operated, and

are entirely clear of the work.

I claim:'

1. In a sewing machine having a base and an,

per end, a lever support guided to move up and down on a portion of the post, a lever pivoted'to said support one. substantially horizontal axis having a knife-carrying .arm extending toward the plane of the work-supporting .end of the post,

on a portion of the post, a lever pivoted 'tosaid support on a substantially 'horizonta'laxis a knife-carrying arm extending toward the plane .of the work-supporting end ,ofthe :post, :a, knife having a cutting edge transverse ,to said :plane mounted on the extremity .of said lever arm in a position adapting it to be'shifted, bymovement of the support, between positions in .whichit Lis, respectively, wholly abelowisaid :plane and where its cutting edge crosses said planejk'and avlever support lifter pivoted on the post below them;- per end thereof and engaged with said ilever support for raising and lowering the same and the lever to put the knife 'intoone or :therother of the before-named.positions.

3. In a sewing machine having .a .base'sand an upright post adapted .to support work on :its zup- ,per end, a lever support guided to move iuprand down on a portioniof thepost, a lever pivoted;to

said support on a substantially horizontal axis ,1

having a knife-carrying arm extending "toward the plane of the work-supporting end of the post, a knife having a cutting edge transverse --to said plane mounted on the extremitywofzsaid lever arm in a position adapting it to be-shiftei.

by movement of the support, between positions in which it is, respectively, WhOllYvbGlOWL-Sflid plane and where its cutting edge crosses isaid plane, and a lever support lifter :pivoted on -;the post below the upper -endthereof and-en a ed with said lever support for raising and lowering the same and the lever toput the knife :intmone or the other of the before-named positions combined with disconnectible ,means for imparting vibrative movement to saidi'lever; 'therlevergsupport lifter having provisions for disconnecting said driving means .from the lever whemtheknife .is placed in inoperative position.

4. A sewing machine including a post a Worksupporting plate mounted 'on the zupperqend of thepost havinga'straight-edge at one side there- .of, -a lever pivotedbelowthe upper end'zof ,the post havingv a rising arm movable in directions "parallel to said edge, alknife carried by the-pp- ,per'end of said lever-arm, disconnectible driving a means for oscillating the lever, and correlated means for lowering said arm and; disconnecting said driving mechanism, and forzraising thetarm and connecting a the driving rmechanism; -.-said knife being located on thelever-so thatt-its scutting edge bearsagainst the straight edge OfqSald plate and crosses theplane ,oithe'supporting edge of the plate when the lever is raised,,-and the knife is wholly below said plane whenthe lever is lowered.

' 5. A trimming attachment for sewin imachines, comprising a supporting structure, .a lever support guided to move in a given path on said supporting structure,-a leverpivoted to said support on amaxis transverse rto -:the direction "of movement of the lever support and having a knife-bearing arm projecting from its pivot in said direction, .a trimming knife carried by said arm, and a lever support lifter havin a cam portion engageable with a-proiection .on the lever support and movable so as to cause shifting of the lever support-in one direction .or th p msite direction its pres ribed p th.

die trimm ng a t chm n as s i r h n combined w t a driv fo vibr ting said leve in disconne tible oup i g betwee the driver and lever. and means ope ted by ai lever, support lifter for disconnecting said couplin when the leve pp rt is lowered and connecting it when the lever support is raised.

,7. A trimming attachment as set forth in claim 5,.eombined with -a vibrating driver for the ov a d se s geablc coup ing we n t e driver and lever consisting of a retractible pin ,carried by one of them entering a slot in the .rothernand a cam element carried by the lever support lifter arranged and operated to retract said pint-mm saidslot when the lever is lowered.

In a sewing machine having a base and a ,post rising from the base,--said post being constructed with a work supporting top member and a detachable .front ,plate, a knife lever supportin guided engagement with the inner side of said plate for movement up and down, a knife lever pivoted to said lever support on a substantially horizontal axis within the post extending toward said Work supporting member, a knife carried by said lever having a cutting edge lying in a plane transverse to said work supporting member and being located for placement above and below the -.work supporting portion of said member by movement up and down of said lever support, and a lifter mounted ,on said front .plate in accessible position for manipulation by anoperator and having alifting portion engagev.ablewitll a part of said lever support for raising the latter from ;a lowered position.

9. In a sewing machine having a base and a .postrising from the base, said post being ,con-

. :structed with ,a work supporting top member and a detachable ,front plate, a knife lever support in lguided engagement with the inner side of said platefor movement up and down, a knife leverpivoted to saidsupp rt on a substanti lly horizontal axiswithin the "post extending toward said supportingmember, a knife carried by said lever :having a cuttingedge lying in aplane transverse to said work supporting member and ,being located for placement above and below the work supporting portionof said member .by movement up and down of said lever support, a i-driving .a-rm independent .of said lever, means for oscillating said driving arm, and a discon- -nectible coupling between said armand lever arranged to transmit movement from the ,arm .to the lever at a point separated from ,the pivot axis of :the latter.

1min a sewing machine having a ,base and apost rising from 13118213356, said post :being constructed with a work supporting :top member ,andra detachable ,front plate, aknife leversupmleverrzhaving a cutting edge lying in a plane :transverselto said work supportingmemberand 'ibeing locatedfor placement above and belowthe work supporting portion of said member by movement up and down of said lever support, a driver for said lever movable back and forth in opposite directions, a disconnectible coupling between said lever and driver for transmitting movement from one to the other, and a lifter movable in opposite directions, said lifter having means for raising the knife lever support from a lowered position when moved in one direction and for disconnecting said coupling when moved in the opposite direction.

11. A sewing machine comprising a base, a post rising from said base having a work supporting plate on its upper end, an oscillative work feeder mounted in thepost extending at its upper end through said plate for engagement with work resting thereon and being movable in a given path for feeding the work, a needle mounted to reciprocate in a path transverse to said plate beside the feeder, a knife lever pivotally supported in the post to swing in a plane parallel to the plane in which the feeder oscillates, a knife carried by said lever located at the opposite side of the needle path from the feeder, means for raising and lowering the pivotal support for said knife lever through a distance sufficient to place the knife edge across a work receiving space above the work support, and below such space, an oscillative driving arm rising from the base adjacent to the knife lever, a disengageable coupling between said arm and lever for transmitting movement from one to the other, and means associated with said raising means for causing disconnection of said coupling when the knife lever is lowered and connection of the coupling when the lever is raised.

12. In a sewing machine having a base, a post rising from said base having a work supporting plate at its top and a front wall, a knife lever support in guided engagement with the inner side of said wall for movement up and down, a

, knife lever in pivotal connection with said support having arms extending upward and downcoupling pin carried by said arm extending into impelling engagement with the lever arm, said lifter and pin having interacting wedge elements cooperatively arranged to retract the coupling pin from engagement with the knife lever when the lifter is turned to cause lowering of the lever support.

13. In a sewing machine having an upright post with a work supporting top member, a knife lever support mounted in said post with provision for up and down movement toward and away from said top member, a knife lever pivoted to said support on a substantially horizontal axis having an arm extending toward said top member, a knife having a shank secured to said arm and a substantially horizontal portion above the arm provided with a cutting edge at its extremity and a separating lip projecting beyond and laterally from said cutting edge, and means for oscillating said lever; the lever support being shiftable between positions, in one of which the knife edge crosses and extends above the upper surface of said top member, and in the other of which the knife and its separating lip are mainly below the said surface.

ARNOLD KROI-IN. 

